Ecumenism is the belief that the different Christian Churches should be as united as possible, and can also be used to refer to actions based on this belief.
[formal]
ecumenism in British English
(ɪˈkjuːməˌnɪzəm, ˈɛkjʊm-), ecumenicism (ˌiːkjʊˈmɛnɪˌsɪzəm, ˌɛk-) or ecumenicalism
noun
the aim of unity among all Christian churches throughout the world
ecumenism in American English
(ˈɛkjuməˌnɪzəm; ˈɛkjəməˌnɪzəm; often ɛˈkjuməˌnɪzəm; ɪˈkjuməˌnɪzəm)
noun
1.
the ecumenical movement among Christian churches
2.
the principles or practice of promoting cooperation or better understanding among differing religious faiths